For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningExterior Lighting
The exterior lamp control is to the left of the steering column on the instrument
panel.
: Briefly turn to this position
to turn the automatic lamp control off or on again.
AUTO: Turns the headlamps on automatically at normal brightness, together with
the parking lamps, taillamps, license ...
Installation Procedure
Prepare all mating surfaces as necessary
Align the body lock pillar outer panel reinforcement.
Drill 8 mm (5/16 in) for plug welding along the edges of the body lock
pillar outer panel reinforcement as noted from the original
panel.
Clean and prepare the attaching surfac ...
Safety Locks
The rear door safety locks prevent passengers from opening the rear doors from
inside the vehicle.
Press to activate the safety locks.
The indicator light comes on when activated.
The rear door power windows are also disabled.
Press again to deactivate the safety
locks and power windows ...